Gas turbine

ABSTRACT

Blade ring cooling passages ( 14, 15 ) are provided inside a first blade ring ( 8 ) and a second blade ring ( 9 ). The blade ring cooling passages ( 14, 15 ) are connected with each other through a communication pipe ( 16 ) that is arranged in an axial direction of the blade ring. From outside of a wheel chamber ( 1 ), cooling air ( 17 ) to cool down stationary blades is sent with pressure into inside of the stationary blades which are installed inner wall of the blade rings. Thermal shields ( 18 ) are provided on outer surfaces of the blade rings ( 14, 15 ) and communication pipes ( 16 ) through gaps therebetween. In the gaps between the outer surfaces of the blade rings ( 8, 9 ) or the outer surfaces of the communication pipes ( 16 ) and the thermal shields ( 18 ), partitions are installed to stagnate the cooling air ( 17 ) to cool down the stationary blades.

TECHNICAL FIELD

[0001] The present invention relates to a gas turbine and moreparticularly to gas turbine blade rings having blade ring coolingpassages to improve effects of thermal shields provided around the bladerings.

BACKGROUND ART

[0002]FIG. 5 is a cross section of an inside of the gas turbine. The gasturbine is used for the convenience of explanation of the presentinvention, and does not belong to the category so-called known art. InFIG. 5, a first blade ring 31 and a second blade ring 32 are separated.The first blade ring 31 and the second blade ring 32 correspond to afirst moving blade 33 and a second moving blade 34, respectively.Circumferential blade ring cooling passages 35 and 36 are providedinside the first blade ring 31 and the second blade ring 32respectively. The cooling passages 35 and 36 are axially connected witheach other through a communication pipe 37.

[0003] From outside of the blade rings 31 and 32 (herein, outside of awheel chamber 38) cooling air 39 to cool down stationary blades isforcefully introduced. The cooling air 39 flows through a space made byan inner wall of the wheel chamber 38 and an outer surface of the bladerings 31 and 32, and eventually flows into inside of a stationary blades40, then exhausted from small holes 41 provided on the surface of thestationary blades.

[0004] Temperature and pressure-controlled steam flows inside thecooling passages 35 and 36. Thereby, the steam optimally maintainsclearance between the first moving blade 33 and an inner wall 42 of thefirst blade ring that opposes the blade 33, and also the clearancebetween the second moving blade 34 and an inner wall 43 of the secondblade ring that opposes the blade 34, while the turbine is running.Meanwhile, if the cooling air 39 hits outer surfaces of the blade rings31, 32, and the communication pipe 37, due to an effect of heattransfer, the cooling air 39 affects the temperature of the steamflowing inside the cooling passages 35 and 36, because the temperatureof the cooling air 39 is different from the temperature of the steam.Thermal shields 44 are provided on the outer surfaces of the blade rings31, 32, and the communication pipe 37, to avoid direct contact of thecooling air 39 with the outer surfaces of the blade rings 31, 32, andthe communication pipe 37.

[0005] It is not appropriate to attach the thermal shields 44 directlyto the blade rings 31 and 32, because the thermal shields 44 are made ofmetal plates, and have a different thermal expansion coefficient from athermal expansion coefficient of the blade rings 31 and 32 at the sametemperature. Thus, the thermal shields 44 are bolted to the outersurfaces of the blade rings 31 and 32 through spacers. By this means,gaps are produced between the outer surfaces of the blade rings 31 and32 and the thermal shields 44. According to the art, a thermal shieldeffectiveness of the thermal shields 44, and air existing in the gaps,enhanced the effects of the thermal shields.

[0006] However, according to the art, there are slight gaps between theouter surfaces of the blade rings and the thermal shields. Therefore, byforced convection (especially, by dynamic pressure) of the cooling airwhich is high-speed and high-pressure, air with a different temperaturefrom the steam temperature, easily and problematically entered into thegaps. If the high-speed air enters into the gaps, a heat transfercoefficient of the outer surface of the blade rings and the likefluctuates, thereby the effect of the thermal shields reduces by half.

[0007] Therefore, it is an object of the present invention to provide agas turbine that effectively controls a loss of heat in the blade ringcooling passages by adding a contrivance to the gaps between the outersurfaces of the blade rings and thermal shields.

DISCLOSURE OF THE INVENTION

[0008] The gas turbine according to the present invention comprises ablade ring; a moving blade which rotates along inside of the blade ring;a stationary blade mounted to an inner wall of the blade ring; a steampassage, provided in the blade ring at a periphery of the moving blade,for flowing temperature-controlled steam for cooling the moving blade;an air passage for taking in cooling air from outside and cooling thestationary blade; a thermal shield provided to the blade ring betweenthe steam passage and the air passage so that the steam flowing in thesteam passage is thermally shielded from the cooling air flowing in theair passage, wherein the thermal shield is attached to a surface of theblade ring with a gap therebetween in such a manner that the cooling airflows in the gap; and a plurality of partitions formed in the gap and onthe surface of the blade ring to stagnate the cooling air.

[0009] The cooling air is to cool down the stationary blade, which isexposed to high-temperature and high-pressure in the turbine. Therefore,the cooling air is supplied in a form of high-speed and high-pressure,from the outer sides of the blade rings. The cooling air contains a lotof dynamic pressure elements, and easily penetrates into the gaps,resulting in a fluctuation of a heat transfer coefficient of the outersurfaces of the blade rings. According to the present invention,fluctuation of the heat transfer coefficient is prevented from occurringby installing partitions in the gaps. The partitions are made by bendingedges of the thermal shields, or installing convex structures whichstick out on the outer surfaces of the blade rings, or installingsticking out attachments on backsides of the thermal shields.

[0010] The gas turbine according to the next invention comprises aplurality of blade rings arranged along an axis of the gas turbine; amoving blade which rotates along inside of each of the blade rings; astationary blade mounted to an inner wall of each of the blade rings; aplurality of steam passages, provided in each of the blade rings at aperiphery of a corresponding moving blade, for flowingtemperature-controlled steam for cooling the corresponding moving blade;an air passage for taking in cooling air from outside and cooling thestationary blades; a communication pipe for connecting two steampassages so that steam from one steam passage flows into another steampassage; a plurality of thermal shields provided to the blade ring andthe communication pipe between the steam passage and the air passage sothat the steam flowing in the steam passage and the communication pipeis thermally shielded from the cooling air flowing in the air passage,wherein the thermal shields are attached to a surface of the blade ringand a surface of the communication pipe with a gap therebetween in sucha manner that the cooling air flows in the gap; and a plurality ofpartitions formed in the gap and on the surface of the blade ring andthe communication pipe to stagnate the cooling air.

[0011] When there are the plural blade rings and each of the blade ringshas its cooling passage, the cooling passages are axially connected withthe communication pipes. Thus, the temperature-controlled steam flowsinto the communication pipes. Therefore, the thermal shields are alsoprovided around the communication pipes so that the cooling air does notdirectly hit the pipes. According to the present invention, partitionsare provided in gaps between outer surfaces of the communication pipesand the thermal shields to stagnate the cooling air. Thereby, thepartitions prevent the cooling air having a high dynamic pressure, fromentering into the gaps. Stagnation of the cooling air preventsfluctuation of the heat transfer coefficient from occurring, andimproves controllability of the steam which flows through the blade ringpassages. The partitions are made by bending edges of the thermalshields, or installing sticking out attachments to the outer surface ofthe blade rings, or installing sticking out attachments to backsides ofthe thermal shields.

[0012] In the gas turbine according to the next invention based on theabove-mentioned invention, the blade ring is cylindrical; and thepartitions stick outwards from the surface of the blade ring along aradial direction of blade, parallel to an axis of the blade ring, andarranged sporadically on a circumference of the blade ring in such amanner that the cooling air that flows along the circumference of theblade ring is stagnant.

[0013] The blade ring and the communication pipe have cylindricalstructures, and are located on the outer circumference of the gasturbine within a wheel chamber. Hereby, a forced convection, generatedby an inflow of the high-speed and high-pressure cooling air tends tohave a circumferential directionality. Furthermore, if a temperaturedifference occurs, a natural convection caused by the temperaturedifference also tends to have the circumferential directionality.

[0014] In the present invention, the partitions have convex structures,and stick out toward radial directions from the outer surfaces of theblade rings and communication pipes which are cylindrical in shape. Thepartitions are installed circumferentially and sporadically, and fill upthe gaps between the outer surfaces of the blade rings or communicationpipes and the thermal shields. Thus, the partitions are capable ofstagnating the cooling air that flows circumferentially.

[0015] In the gas turbine according to the next invention based on theabove-mentioned invention, the blade ring is cylindrical; and thepartitions stick outwards from the surface of the blade ring along aradial direction of blade ring, perpendicular to an axis of the bladering, and arranged continuously on a circumference of the blade ring insuch a manner that the cooling air that flows along the axis of theblade ring is stagnant.

[0016] In the present invention, partitions have convex structures thatstick out to the radial direction of the outer surfaces of thecylindrical blade rings and the communication pipes. As described above,the forced convection, generated by the cooling air, tends to havedirectionality along circumferential directions of each structure.However, the cooling air involves high-speed turbulent elements. Ifcontinuous partitions are installed circumferentially in the gapsbetween the outer surfaces of the blade rings or communication pipes andthe thermal shields, speed elements of the cooling air reduce. Thus,partitions prevent the cooling air from penetrating, due to dynamicpressure, into the gaps.

[0017] In the gas turbine according to the next invention based on theabove-mentioned invention, the blade ring is cylindrical; and thepartitions stick outwards from the surface of the blade ring along aradial direction of blade ring and are arranged in desired directionswith respect to an axis of the blade ring on in such a manner that thecooling air that flows along any directions is stagnant.

[0018] In the present invention, the partitions have convex structuresthat stick out into the radial directions of the outer surfaces of thecylindrical blade rings and communication pipes. Therefore, byinstalling a plurality of partitions in different directions, it ispossible to stagnate the stationary blade cooling air that flows intothe radial directions and the circumferential directions in the outersurfaces of the blade rings and communication pipes. Further, thedirections of the partitions do not necessarily have to be in parallelwith the axial directions or circumferential directions. The partitionsmay be installed at an angle to the axial directions.

[0019] The gas turbine according to the next invention based on theabove-mentioned invention, the thermal shields are supported by thepartitions.

[0020] In the convex structures in which the partitions stick out fromthe outer surfaces of the blade rings and communication pipes, thesupporting legs which stick out from the thermal shield toward opposingblade rings can exert the same effects as the partitions. Therefore, thecooling air that penetrates into the gaps can be stagnated by installingthe supporting legs in circumferential directions sporadically,continuously, or in different directions in a plurality.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 shows a cross section of an inside of a gas turbineaccording to an embodiment of the present invention;

[0022]FIG. 2 shows an external appearance of the partitions installed onthe outer surfaces of the blade rings and the communication pipes, (a)is a side view, (b) is a front view, (c) is an enlarged view of thecommunication pipe in (a);

[0023]FIG. 3 shows an example of an external appearance of a modifiedform of the partitions, (a) is a side view, (b) is a front view, (c) isan enlarged view of the communication pipe in (a);

[0024]FIG. 4 shows another example of an external appearance of amodification form of the partitions, (a) is a side view, (b) is a frontview, (c) is an enlarged view of the communication pipe in (a); and

[0025]FIG. 5 shows a cross section of an inside of the gas turbine.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] The invention will be explained in detail with reference to theaccompanying drawings. However, the invention is not limited to thatexplained in the embodiment.

[0027] First Embodiment:

[0028]FIG. 1 is a cross section of an inside of a gas turbine accordingto the first embodiment of the present invention. In a wheel chamber 1of the gas turbine, stationary blades 2, 3, and 4 and moving blades 5,6, and 7 are arranged in several stages. Cylindrically-shaped bladerings 8, 9, and 10 are fitted in the wheel chamber, and hold stationaryblades 2, 3, 4 and possess opposing portions 11, 12, and 13. The bladerings 8, 9, and 10 are assembled in connection with each other in anaxial direction.

[0029] Blade ring cooling passages 14 and 15 are provided in each of thefirst blade ring 8, and second stage blade ring 9 to allowtemperature-controlled steam to flow in the cooling passages. Thecooling passages 14 and 15 are connected with each other bycommunication pipes 16 in axial directions. In general, thecommunication pipes 16 are provided around the blade rings 8 and 9 incircumferential directions in a plurality. From outside of the wheelchamber 1, the cooling air 17, which cools down the stationary blades,is taken in and forcefully sent into internal parts of the stationaryblades. The cooling air 17 is not necessarily taken in from outside ofthe wheel chamber, but may also be sent from a compressor of the gasturbine to the outside of the blade rings via inside of the wheelchamber.

[0030] The steam flowing through the cooling passages 14 and 15 istemperature-controlled to optimally maintain the clearance between theperipheries of the moving blades 5, 6 and the portion 11 and 12 whichoppose the peripheries of the moving blades while the turbine isrunning. On the other hand, the cooling air 17 is to cool down thestationary blades which are exposed to high-temperature andhigh-pressure atmosphere in the turbine. The temperature of the coolingair is irrespectively different form the temperature of the steam. Asshown in FIG. 1, the stationary blades cooling air 17 is sent to insideof the stationary blade 3 through the space where blade rings 8, 9 andthe communication pipes 16 are mounted in the wheel chamber 1.Therefore, if the cooling air 17 hits the blade rings 8, 9 orcommunication pipe 16, the air turns into a disturbance and adverselyaffects the temperature-control of the steam. Therefore, the thermalshields 18 are mounted through gaps to the outer surfaces of the bladerings 8, 9 and communication pipes 16.

[0031] The partitions 19 are provided in the gaps between the outersurfaces of the blade rings 8, 9 and communication pipes 16 to stagnatethe cooling air. The partitions 19 prevent the cooling air 17 flowinginto the turbine at a high-speed and having a high dynamic pressure,from penetrating into the gaps. If the cooling air is stagnated,fluctuation of the heat transfer coefficient is prevented from occurringto improve controllability of the temperature of the steam which flowsin the blade ring cooling passages.

[0032]FIG. 2 shows an external appearance of the partitions installed onthe outer surfaces of the blade rings and the communication pipes. InFIG. 2, (a) is a side view, (b) is a front view, (c) is an enlarged viewof the communication pipe in (a). FIG. 2 shows a state that thermalshields are removed for the sake of explanation. The partitions 20 stickout to the radial directions of the blade rings 8, and 9, andcommunication pipes 16 on which the partitions 20 are installed.Further, the partitions 20 are installed sporadically in thecircumferential directions of the blade rings 8, and 9, andcommunication pipes 16.

[0033] Numbers of the partitions are not limited to the numbers shown inFIG. 2. The numbers are properly chosen depending on the dynamicpressure of the cooling air and the place where the cooling air is takenin. In FIG. 2, the partitions are installed almost in the axialdirections, but the directions are not limited to the axial directions.The partitions may be installed at an angle to the axial directions.Further, if the thermal shields are bolted on the top of theconvex-structured partitions, attaching of the thermal shields becomesconvenient. Furthermore, the convex-structured partitions 20 may beinstalled as attachment legs of the thermal shields.

[0034] The forced convection, generated by inflow of the high-speed andhigh-pressure stationary blade cooling air from outside of the bladerings, tends to have a circumferential directionality with respect toeach construction. Furthermore, if a temperature difference occurs, anatural convection caused by the temperature difference also tends tohave the circumferential directionality. The partitions 20 fill in thegaps between the outer surface of the blade rings or communication pipesand the thermal shields, and are able to stagnate the circumferentialflow of the cooling air.

[0035] As explained above, according to the gas turbine of theembodiment, the convex structures are built in circumferentialdirections sporadically, in the gaps between the outer surfaces of theblade rings or communication pipes. Hereby, it is possible to stagnatethe air that exists in the gaps between the outer surface of the bladerings and the thermal shields. Thus, it is possible to reduce thedisturbance generated by the contact of the cooling air with the bladering passages in which temperature-controlled steam flows.

[0036] According to the gas turbine, heat loss at the blade ring coolingpassages becomes substantially controllable, which is impossible by thethermal shields alone. If the temperature control of the steam isperformed properly, without the disturbance of the cooling air, theclearance between the moving blades and the opposing blade rings aremaintained optimally, thus, the turbine efficiencies improve.

[0037] First Modification:

[0038]FIG. 3 shows an example of a modification of an externalappearance of the partitions installed on the outer surfaces of theblade rings and communication pipes. In the FIG. 3, (a) is a side view,(b) is a front view, (c) is an enlarged view of the communication pipein (a). FIG. 3 shows a state that thermal shields are removed just thesame as FIG. 2. In the first modification, partitions 21 stick out tothe radial directions of the blade rings 8, and 9, and the communicationpipes 16 on which the partitions 21 are installed, just the same as thefirst embodiment.

[0039] According to the first modification, the partitions 21 arecontinuously installed on the blade rings 8 and 9 and the communicationpassage 16 in the circumferential directions. Numbers of the partitionsare not limited to the numbers shown in FIG. 3. The numbers are properlychosen depending on the dynamic pressure of the stationary bladescooling air and the place where the cooling air is taken in. In FIG. 3,the partitions are installed in the circumferential directions, but thedirections are not limited to the circumferential directions. Thepartitions may be installed at an angle to the circumferentialdirections. Further, if the thermal shields are bolted on the top of theconvex-structured partitions, attaching of the thermal shields becomesconvenient. Furthermore, the convex-structured partitions 21 may beinstalled as attachment legs of the thermal shields.

[0040] The forced convection, generated by the cooling air of thestationary blades tends to have the directionality in thecircumferential directions of the blade rings 8, 9 and the communicationpipe 16. However, the cooling air involves the high-speed turbulentelements. If the continuous partitions are provided in the gaps betweenthe outer surface of the blade rings 8, 9 and communication pipes 16,the speed element of the cooling air reduces, thus, it is possible toprevent the cooling air from penetrating into the gaps, which mayotherwise occur due to the dynamic pressure of the cooling air.

[0041] As explained above according to the first modification, the gasturbine is provided with the continuous convex-structured partitions inthe gaps between the outer surface of the blade rings or the outersurface of the communication pipes and the thermal shields, it ispossible to stagnate the air existing in the gaps. Thereby, the effectsof the stationary blades cooling air against the blade ring coolingpassages in which the temperature-controlled steam flows can be reduced.

[0042] According to the gas turbine, the heat loss at the blade ringcooling passages becomes substantially controllable, which is notpossible by the thermal shields alone. If the temperature control of thesteam is performed properly, without the disturbance of the cooling air,the clearance between the moving blades and the opposing blade rings aremaintained optimally, thus, the turbine efficiencies improve.

[0043] Second Modification:

[0044]FIG. 4 shows an example of a second modification of an externalappearance of the partitions installed on the outer surfaces of theblade rings and communication pipes. In the FIG. 4, (a) is a side view,(b) is a front view, (c) is an enlarged view of the communication pipein (a). FIG. 4 shows a state that thermal shields are removed just thesame as FIG. 2 and FIG. 3. In the second modification also, partitions22 stick out to the radial directions of the blade rings 8, and 9, andthe communication pipes 16 on which the partitions are installed, andthe partitions are the convex-structured just the same as the embodimentof the first modification.

[0045] Further, the partitions 22 are installed in different directionsin a plurality, and stagnate the air existing in the gaps between theouter surfaces of the blade rings 8, 9, or the outer surface of thecommunication pipes 16, and the thermal shields. In FIG. 4, thepartitions 22 are installed in two directions, that is, in the axialdirections and in the circumferential directions, and the partitionsinstalled two different directions are united. However, as far as theair can be stagnated, there is no need to unite the two differentdirections of partitions. Furthermore, the partitions should notnecessarily be installed in the axial or circumferential directions. Thepartitions may be installed at an angle to the axial or circumferentialdirection. Further, if the thermal shields are bolted on the top of theconvex-structured partitions 22, attaching of the thermal shieldsbecomes convenient. Furthermore, the convex-structured partitions 22 maybe installed as attachment legs of the thermal shields.

[0046] According to the second modification, the gas turbine is providedwith the convex-structured partitions in the gaps between the outersurface of the blade rings or outer surface of the communication pipesand the thermal shields, it is possible to stagnate the air existing inthe gaps. Thereby, the effects of the stationary blade cooling airagainst the bade ring cooling passages in which thetemperature-controlled steam flows can be reduced.

[0047] According to the gas turbine, the heat loss at the blade ringcooling passages becomes substantially controllable, which is notpossible by the thermal shields alone. If the temperature control of thesteam is performed properly, without the disturbance of the cooling air,the clearance between the moving blades and the opposing blade rings aremaintained optimally, thus, the turbine efficiencies improve.

[0048] As explained above, according to the gas turbine of the presentinvention, the partitions to stagnate the stationary blade cooling airare provided in the gaps between the outer surface of the blade ringsand the thermal shields. Therefore, it is possible to reduce thedisturbance generated by the contact of the cooling air with the bladering cooling passages in which the temperature-controlled air flows.Thereby, heat loss at the blade ring cooling passages becomessubstantially controllable, which is impossible by the thermal shieldsalone. If the temperature control of the steam is performed properly,without the disturbance of the cooling air, the clearance between themoving blades and the opposing blade rings are maintained optimally,thus, the turbine efficiencies improve.

[0049] According to the gas turbine of the next invention, thepartitions are provided in the gaps between the outer surface of thecommunication pipes and the thermal shields, it is possible to reducethe disturbance generated by the contact of the cooling air with theblade ring cooling passages in which the temperature-controlled airflows. Thereby, the heat loss at the blade ring cooling passages becomessubstantially controllable, which is impossible by the thermal shieldsalone. If the temperature control of the steam is performed properly,without the disturbance of the cooling air, the clearance between themoving blades and the opposing blade rings are maintained optimally,thus, the turbine efficiencies improve.

[0050] According to the gas turbine of the next invention, it ispossible to stagnate the air existing in the gaps between the outersurfaces of the blade rings and the thermal shields, because thesporadic convex-structured partitions are provided in circumferentialdirections in the gaps between the outer surfaces of the blade rings orcommunication pipes and the thermal shields. Thereby, the disturbancecaused by the contact of the stationary blade cooling air with the bladering cooling passages in which the temperature-controlled steam flows,can be reduced. Thus, the heat loss at the blade ring cooling passagesbecomes substantially controllable, which is impossible by the thermalshields alone. If the temperature control of the steam is performedproperly, without the disturbance of the cooling air, the clearancebetween the moving blades and the opposing blade rings are maintainedoptimally, thus, the turbine efficiencies improve.

[0051] According to the gas turbine of the next invention, it ispossible to stagnate the air existing in the gaps between the outersurfaces of the blade rings or communication pipes and the thermalshields, because the continuous convex-structured partitions areprovided in circumferential directions in the gaps between the outersurfaces of the blade rings or communication pipes and the thermalshields. Thereby, influences of the blade ring cooling air against theblade ring cooling passages in which the temperature-controlled steamflows can be reduced. Thus, the heat loss at the blade ring coolingpassages becomes substantially controllable which is impossible by thethermal shields alone. If the temperature control of the steam isperformed properly, without the disturbance of the stationary bladecooling air, the clearance between the moving blades and the opposingblade rings are maintained optimally, thus, the turbine efficienciesimprove.

[0052] According to the gas turbine of the next invention, it ispossible to stagnate the air existing in the gaps between the outersurfaces of the blade rings or communication pipes and the thermalshields, because the convex-structured partitions are provided indifferent directions and in a plurality in the gaps between the outersurfaces of the blade rings or communication pipes and the thermalshields. Thereby, it is possible to reduce the influences of thestationary blade cooling air against the blade ring cooling passages inwhich the temperature-controlled steam flows. Thus, the heat loss at theblade ring cooling passages becomes substantially controllable, which isimpossible by the thermal shields alone. If the temperature control ofthe steam is performed properly, without the disturbance of the coolingair, the clearance between the moving blades and the opposing bladerings are maintained optimally, thus, the turbine efficiencies improve.

[0053] According to the gas turbine of the next invention, it ispossible to stagnate the air existing in the gaps between the outersurfaces of the blade rings or communication pipes and the thermalshields, because the sticking out convex-structured partitions areprovided as attachment legs on the face of the thermal shields whichface the blade rings. If the air stagnates, it becomes possible toreduce the disturbance caused by the contact of the cooling air with theblade ring passages in which temperature-controlled steam flows. Thus,the heat loss at the blade ring cooling passages becomes substantiallycontrollable, which is impossible by the thermal shields alone. If thetemperature control of the steam is performed properly, without thedisturbance of the cooling air, the clearance between the moving bladesand the opposing blade rings are maintained optimally, thus, the turbineefficiencies improve.

INDUSTRIAL APPLICABILITY

[0054] The gas turbine according to the present invention is suitable inimproving efficiencies of the blade rings, having cooling passages, andthe thermal shields, which are provided around the blade rings.

1. A gas turbine comprising: a blade ring; a moving blade which rotatesalong inside of the blade ring; a stationary blade mounted to an innerwall of the blade ring; a steam passage, provided in the blade ring at aperiphery of the moving blade, for flowing temperature-controlled steamfor cooling the moving blade; an air passage for taking in cooling airfrom outside and cooling the stationary blade; a thermal shield providedto the blade ring between the steam passage and the air passage so thatthe steam flowing in the steam passage is thermally shielded from thecooling air flowing in the air passage, wherein the thermal shield isattached to a surface of the blade ring with a gap therebetween in sucha manner that the cooling air flows in the gap; and a plurality ofpartitions formed in the gap and on the surface of the blade ring tostagnate the cooling air.
 2. A gas turbine comprising: a plurality ofblade rings arranged along an axis of the gas turbine; a moving bladewhich rotates along inside of each of the blade rings; a stationaryblade mounted to an inner wall of each of the blade rings; a pluralityof steam passages, provided in each of the blade rings at a periphery ofa corresponding moving blade, for flowing temperature-controlled steamfor cooling the corresponding moving blade; an air passage for taking incooling air from outside and cooling the stationary blades; acommunication pipe for connecting two steam passages so that steam fromone steam passage flows into another steam passage; a plurality ofthermal shields provided to the blade ring and the communication pipebetween the steam passage and the air passage so that the steam flowingin the steam passage and the communication pipe is thermally shieldedfrom the cooling air flowing in the air passage, wherein the thermalshields are attached to a surface of the blade ring and a surface of thecommunication pipe with a gap therebetween in such a manner that thecooling air flows in the gap; and a plurality of partitions formed inthe gap and on the surface of the blade ring and the communication pipeto stagnate the cooling air.
 3. The gas turbine according to claim 1 or2, wherein the blade ring is cylindrical; and the partitions stickoutwards from the surface of the blade ring along a radial direction ofblade, parallel to an axis of the blade ring, and arranged sporadicallyon a circumference of the blade ring in such a manner that the coolingair that flows along the circumference of the blade ring is stagnant. 4.The gas turbine according to claim 1 or 2, wherein the blade ring iscylindrical; and the partitions stick outwards from the surface of theblade ring along a radial direction of blade ring, perpendicular to anaxis of the blade ring, and arranged continuously on a circumference ofthe blade ring in such a manner that the cooling air that flows alongthe axis of the blade ring is stagnant.
 5. The gas turbine according toclaim 1 or 2, wherein the blade ring is cylindrical; and the partitionsstick outwards from the surface of the blade ring along a radialdirection of blade ring and are arranged in desired directions withrespect to an axis of the blade ring on a circumference of the bladering in such a manner that the cooling air that flows along anydirections is stagnant.
 6. The gas turbine according to claim 1 or 2,wherein the thermal shields are supported by the partitions.